Microphones are ubiquitous devices that convert acoustic signals to electric signals and can be found in many devices, including telephones, tape recorders, hearing aids, etc., wherein the choice of transducer is often determined by the particular sound or environment in which the transducer is employed.
For example, condenser or capacitor microphones employ a diaphragm that acts as one plate of a capacitor, in which vibrations caused by impinging sound produce changes in the distance between the capacitor plates. A similar principle is used in electret condenser microphones in which a permanently electrically charged or polarized dielectric material is part of the capacitor circuit. In other examples, a dynamic microphone uses a small and movable coil that is positioned in the magnetic field of a permanent magnet, wherein the coil is attached to the diaphragm. Similarly, a ribbon microphone employs a thin, usually corrugated metal ribbon that is suspended in a magnetic field, wherein the ribbon is electrically connected to the microphone output. Vibration of the ribbon within the magnetic field generates the electrical signal. In yet another class of microphones, piezoelectric materials are employed in which the sound pressure impinging onto the material produces a voltage across the material.
However, almost all of the known microphones are designed to operate in a particular SPL (sound pressure level) range and will therefore either be sensitive to low SPL and distort at high SPL or tolerate high SPL at the expense of sensitivity to low SPL sounds. Still further, at SPL of above 90 db, compression is typically required, or distortion will significantly increase. Further disadvantages are encountered in most microphones with respect to directionality. Most typically, directionality is achieved by housing design such that at least some of the off-axis sound waves are canceled or reduced. Unfortunately, and especially where high directionality is desirable, the design of such microphones often limits the range of uses.
Therefore, while numerous microphones are known in the art, all or almost all of them suffer from one or more disadvantages. Consequently, there is still a need to provide improved configurations and methods for improved microphones, especially where large dynamic range and/or directionality are desired.